Common Linux Command-Line Tools

Basic Linux Commands

Welcome to this general tutorial on basic Linux commands. To get started you
will need a Linux Distribution. Thats it. All Distributions come with a shell
enviornment, whether its a desktop-interface-shell like mate-terminal (like i
use) to an initial command line if you dont have a desktop manager. This is a
very common method of getting around your file system and doing routine
maintenance on your Linux Distribution. I am currently using Debian 10, with
mate desktop enviornment installed , and i use the mate-terminal which i believe
sets me up with a BASH enviornment . I would also like to mention if you go to
google and type :
man program_name
you will get a detailed manual of the program with command line flags and
usable variables.

1. pwd:

pwd stands for print working directory. this will tell you where you are in
your file system. There is a couple flags you can type in to manipulate this, for example the
“-L” or “–logical” flag uses PWD from the enviornment, even if it contains
symlinks. If you use “-P” or “–physical” it will avoid all symlinks. You can
also type “–help” to display the options.

clim@debian:~/Desktop/Tests$ pwd --help
pwd: pwd [-LP]
    Print the name of the current working directory.

    Options:
      -L	print the value of $PWD if it names the current working
    		directory
      -P	print the physical directory, without any symbolic links

    By default, `pwd' behaves as if `-L' were specified.

    Exit Status:
    Returns 0 unless an invalid option is given or the current directory
    cannot be read.
clim@debian:~/Desktop/Tests$ pwd
/home/clim/Desktop/Tests
clim@debian:~/Desktop/Tests$ 

2. ls:
ls is a command which will list the files in your current directory and sorts
them alphabetically or by other attributes based on commandline flags. This will
also list hidden files in your current directory if you give the -a flag. If you
want more information about the ls command, you can type “ls –help” to get all
the flags you can use.

clim@debian:~$ ls
bin      diff.txt   info.err  nano.save  Pictures    src
Cpp      Documents  Libre-OS  obj        Public      Templates
Desktop  Downloads  Music     opt        remove.txt  Videos
clim@debian:~$ ls -a
.              Downloads      .nuget           .themes
..             .emacs.d       obj              .var
.atom          .gconf         opt              .vboxclient-clipboard.pid
.bash_history  .gnome2        Pictures         .vboxclient-display.pid
.bash_logout   .gnupg         .pki             .vboxclient-draganddrop.pid
.bashrc        .ICEauthority  .profile         .vboxclient-seamless.pid
bin            .icons         Public           Videos
.cache         info.err       .recently-used   .viminfo
.config        Libre-OS       remove.txt       .Xauthority
Cpp            .local         src              .xsession-errors
Desktop        .mozilla       .ssh             .xsession-errors.old
diff.txt       Music          .swp
.dmrc          .nano          .templateengine
Documents      nano.save      Templates
clim@debian:~$ 

3. cd

cd stands for Change Directories. This will move you to to the directory you
specify. This has similar flags to the pwd command. You can supply it “-L” to
force symbolic links to be followed. This is the default flag that gets used if
no other flag is specified. The Next flag is “-P” which use the physical
directory structure without following symbolic links. The “-e” is given if the
“-P” flag is specified. If the current working directory cannot be determined
(For example, you tried to change to a symbolic link even tho you specified
“-P”) then the exit status will return a non-zero number. And last, on systems
that support it, “-@” will create a file with extended attributes as a directory
containing the file attributes. All of this information is provided by
“cd –help”.

clim@debian:~$ ls
bin      diff.txt   info.err  nano.save  Pictures    src
Cpp      Documents  Libre-OS  obj        Public      Templates
Desktop  Downloads  Music     opt        remove.txt  Videos
clim@debian:~$ cd Documents/
clim@debian:~/Documents$ ls
Project
clim@debian:~/Documents$ cd Project/
clim@debian:~/Documents/Project$ ls
ServerProgram
clim@debian:~/Documents/Project$ cd ../../Public
clim@debian:~/Public$ ls
clim@debian:~/Public$ cd ../
clim@debian:~$ 

4. touch

touch will update the access and modification times of each specified file to
the current time. This is useful if you want to quickly create a file. The
following is supplied using “touch –help”

clim@debian:~$ touch --help
Usage: touch [OPTION]... FILE...
Update the access and modification times of each FILE to the current time.

A FILE argument that does not exist is created empty, unless -c or -h
is supplied.

A FILE argument string of - is handled specially and causes touch to
change the times of the file associated with standard output.

Mandatory arguments to long options are mandatory for short options too.
  -a                     change only the access time
  -c, --no-create        do not create any files
  -d, --date=STRING      parse STRING and use it instead of current time
  -f                     (ignored)
  -h, --no-dereference   affect each symbolic link instead of any referenced
                         file (useful only on systems that can change the
                         timestamps of a symlink)
  -m                     change only the modification time
  -r, --reference=FILE   use this file's times instead of current time
  -t STAMP               use [[CC]YY]MMDDhhmm[.ss] instead of current time
      --time=WORD        change the specified time:
                           WORD is access, atime, or use: equivalent to -a
                           WORD is modify or mtime: equivalent to -m
      --help     display this help and exit
      --version  output version information and exit

Note that the -d and -t options accept different time-date formats.

GNU coreutils online help: 
Full documentation at: 
or available locally via: info '(coreutils) touch invocation'
clim@debian:~$ 
clim@debian:~$ ls
bin      diff.txt   info.err  nano.save  Pictures    src
Cpp      Documents  Libre-OS  obj        Public      Templates
Desktop  Downloads  Music     opt        remove.txt  Videos
clim@debian:~$ touch testTouch
clim@debian:~$ ls
bin      diff.txt   info.err  nano.save  Pictures    src        Videos
Cpp      Documents  Libre-OS  obj        Public      Templates
Desktop  Downloads  Music     opt        remove.txt  testTouch
clim@debian:~$ 

5. cat
This program concatenates files to standard output . This is useful for when
you are checking the contents of a file.

clim@debian:~$ ls
bin      diff.txt   info.err  nano.save  Pictures    src        testTouch
Cpp      Documents  Libre-OS  obj        Public      Templates  Videos
Desktop  Downloads  Music     opt        remove.txt  testCat
clim@debian:~$ cat testCat 
Hello from testCat
clim@debian:~$ 

Here is the help page of cat:

clim@debian:~$ cat --help
Usage: cat [OPTION]... [FILE]...
Concatenate FILE(s) to standard output.

With no FILE, or when FILE is -, read standard input.

  -A, --show-all           equivalent to -vET
  -b, --number-nonblank    number nonempty output lines, overrides -n
  -e                       equivalent to -vE
  -E, --show-ends          display $ at end of each line
  -n, --number             number all output lines
  -s, --squeeze-blank      suppress repeated empty output lines
  -t                       equivalent to -vT
  -T, --show-tabs          display TAB characters as ^I
  -u                       (ignored)
  -v, --show-nonprinting   use ^ and M- notation, except for LFD and TAB
      --help     display this help and exit
      --version  output version information and exit

Examples:
  cat f - g  Output f's contents, then standard input, then g's contents.
  cat        Copy standard input to standard output.

GNU coreutils online help: 
Full documentation at: 
or available locally via: info '(coreutils) cat invocation'
clim@debian:~$ 

6. mkdir
mkdir is used to make directories. Whenever i setup a new programming project
this is the first command i use, to keep my project isolated. It has multiple
command-line arguments you can pass in. Here is the help argument:

clim@debian:~$ mkdir --help
Usage: mkdir [OPTION]... DIRECTORY...
Create the DIRECTORY(ies), if they do not already exist.

Mandatory arguments to long options are mandatory for short options too.
  -m, --mode=MODE   set file mode (as in chmod), not a=rwx - umask
  -p, --parents     no error if existing, make parent directories as needed
  -v, --verbose     print a message for each created directory
  -Z                   set SELinux security context of each created directory
                         to the default type
      --context[=CTX]  like -Z, or if CTX is specified then set the SELinux
                         or SMACK security context to CTX
      --help     display this help and exit
      --version  output version information and exit

GNU coreutils online help: 
Full documentation at: 
or available locally via: info '(coreutils) mkdir invocation'
clim@debian:~$ ^C

For the next few, i will let the help prompts speak for them:

7. rmdir

clim@debian:~$ rmdir --help
Usage: rmdir [OPTION]... DIRECTORY...
Remove the DIRECTORY(ies), if they are empty.

      --ignore-fail-on-non-empty
                  ignore each failure that is solely because a directory
                    is non-empty
  -p, --parents   remove DIRECTORY and its ancestors; e.g., 'rmdir -p a/b/c' is
                    similar to 'rmdir a/b/c a/b a'
  -v, --verbose   output a diagnostic for every directory processed
      --help     display this help and exit
      --version  output version information and exit

GNU coreutils online help: 
Full documentation at: 
or available locally via: info '(coreutils) rmdir invocation'
clim@debian:~$ 

8. cp
This command is used specifically to copy files.

  clim@debian:~$ cp --help
  Usage: cp [OPTION]... [-T] SOURCE DEST
    or:  cp [OPTION]... SOURCE... DIRECTORY
    or:  cp [OPTION]... -t DIRECTORY SOURCE...
  Copy SOURCE to DEST, or multiple SOURCE(s) to DIRECTORY.

  Mandatory arguments to long options are mandatory for short options too.
    -a, --archive                same as -dR --preserve=all
        --attributes-only        don't copy the file data, just the attributes
        --backup[=CONTROL]       make a backup of each existing destination file
    -b                           like --backup but does not accept an argument
        --copy-contents          copy contents of special files when recursive
    -d                           same as --no-dereference --preserve=links
    -f, --force                  if an existing destination file cannot be
                                   opened, remove it and try again (this option
                                   is ignored when the -n option is also used)
    -i, --interactive            prompt before overwrite (overrides a previous -n
                                    option)
    -H                           follow command-line symbolic links in SOURCE
    -l, --link                   hard link files instead of copying
    -L, --dereference            always follow symbolic links in SOURCE
    -n, --no-clobber             do not overwrite an existing file (overrides
                                   a previous -i option)
    -P, --no-dereference         never follow symbolic links in SOURCE
    -p                           same as --preserve=mode,ownership,timestamps
        --preserve[=ATTR_LIST]   preserve the specified attributes (default:
                                   mode,ownership,timestamps), if possible
                                   additional attributes: context, links, xattr,
                                   all
        --no-preserve=ATTR_LIST  don't preserve the specified attributes
        --parents                use full source file name under DIRECTORY
    -R, -r, --recursive          copy directories recursively
        --reflink[=WHEN]         control clone/CoW copies. See below
        --remove-destination     remove each existing destination file before
                                   attempting to open it (contrast with --force)
        --sparse=WHEN            control creation of sparse files. See below
        --strip-trailing-slashes  remove any trailing slashes from each SOURCE
                                   argument
    -s, --symbolic-link          make symbolic links instead of copying
    -S, --suffix=SUFFIX          override the usual backup suffix
    -t, --target-directory=DIRECTORY  copy all SOURCE arguments into DIRECTORY
    -T, --no-target-directory    treat DEST as a normal file
    -u, --update                 copy only when the SOURCE file is newer
                                   than the destination file or when the
                                   destination file is missing
    -v, --verbose                explain what is being done
    -x, --one-file-system        stay on this file system
    -Z                           set SELinux security context of destination
                                   file to default type
        --context[=CTX]          like -Z, or if CTX is specified then set the
                                   SELinux or SMACK security context to CTX
        --help     display this help and exit
        --version  output version information and exit

  By default, sparse SOURCE files are detected by a crude heuristic and the
  corresponding DEST file is made sparse as well.  That is the behavior
  selected by --sparse=auto.  Specify --sparse=always to create a sparse DEST
  file whenever the SOURCE file contains a long enough sequence of zero bytes.
  Use --sparse=never to inhibit creation of sparse files.

  When --reflink[=always] is specified, perform a lightweight copy, where the
  data blocks are copied only when modified.  If this is not possible the copy
  fails, or if --reflink=auto is specified, fall back to a standard copy.
  Use --reflink=never to ensure a standard copy is performed.

  The backup suffix is '~', unless set with --suffix or SIMPLE_BACKUP_SUFFIX.
  The version control method may be selected via the --backup option or through
  the VERSION_CONTROL environment variable.  Here are the values:

    none, off       never make backups (even if --backup is given)
    numbered, t     make numbered backups
    existing, nil   numbered if numbered backups exist, simple otherwise
    simple, never   always make simple backups

  As a special case, cp makes a backup of SOURCE when the force and backup
  options are given and SOURCE and DEST are the same name for an existing,
  regular file.

  GNU coreutils online help: 
  Full documentation at: 
  or available locally via: info '(coreutils) cp invocation'
  clim@debian:~$ 

9. rm
If i need to remove a file, i can simply use the rm command.

clim@debian:~$ rm --help
Usage: rm [OPTION]... [FILE]...
Remove (unlink) the FILE(s).

  -f, --force           ignore nonexistent files and arguments, never prompt
  -i                    prompt before every removal
  -I                    prompt once before removing more than three files, or
                          when removing recursively; less intrusive than -i,
                          while still giving protection against most mistakes
      --interactive[=WHEN]  prompt according to WHEN: never, once (-I), or
                          always (-i); without WHEN, prompt always
      --one-file-system  when removing a hierarchy recursively, skip any
                          directory that is on a file system different from
                          that of the corresponding command line argument
      --no-preserve-root  do not treat '/' specially
      --preserve-root[=all]  do not remove '/' (default);
                              with 'all', reject any command line argument
                              on a separate device from its parent
  -r, -R, --recursive   remove directories and their contents recursively
  -d, --dir             remove empty directories
  -v, --verbose         explain what is being done
      --help     display this help and exit
      --version  output version information and exit

By default, rm does not remove directories.  Use the --recursive (-r or -R)
option to remove each listed directory, too, along with all of its contents.

To remove a file whose name starts with a '-', for example '-foo',
use one of these commands:
  rm -- -foo

  rm ./-foo

Note that if you use rm to remove a file, it might be possible to recover
some of its contents, given sufficient expertise and/or time.  For greater
assurance that the contents are truly unrecoverable, consider using shred.

GNU coreutils online help: 
Full documentation at: 
or available locally via: info '(coreutils) rm invocation'
clim@debian:~$ 

10. mv
Unlike the cp command which copies files, the mv will move the files completely
to the destination.

clim@debian:~$ mv --help
Usage: mv [OPTION]... [-T] SOURCE DEST
  or:  mv [OPTION]... SOURCE... DIRECTORY
  or:  mv [OPTION]... -t DIRECTORY SOURCE...
Rename SOURCE to DEST, or move SOURCE(s) to DIRECTORY.

Mandatory arguments to long options are mandatory for short options too.
      --backup[=CONTROL]       make a backup of each existing destination file
  -b                           like --backup but does not accept an argument
  -f, --force                  do not prompt before overwriting
  -i, --interactive            prompt before overwrite
  -n, --no-clobber             do not overwrite an existing file
If you specify more than one of -i, -f, -n, only the final one takes effect.
      --strip-trailing-slashes  remove any trailing slashes from each SOURCE
                                 argument
  -S, --suffix=SUFFIX          override the usual backup suffix
  -t, --target-directory=DIRECTORY  move all SOURCE arguments into DIRECTORY
  -T, --no-target-directory    treat DEST as a normal file
  -u, --update                 move only when the SOURCE file is newer
                                 than the destination file or when the
                                 destination file is missing
  -v, --verbose                explain what is being done
  -Z, --context                set SELinux security context of destination
                                 file to default type
      --help     display this help and exit
      --version  output version information and exit

The backup suffix is '~', unless set with --suffix or SIMPLE_BACKUP_SUFFIX.
The version control method may be selected via the --backup option or through
the VERSION_CONTROL environment variable.  Here are the values:

  none, off       never make backups (even if --backup is given)
  numbered, t     make numbered backups
  existing, nil   numbered if numbered backups exist, simple otherwise
  simple, never   always make simple backups

GNU coreutils online help: 
Full documentation at: 
or available locally via: info '(coreutils) mv invocation'

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s